India's crude imports from Iran rose by a third in the first half of the year, data from trade sources showed, after the shipments were boosted following an interim deal to slow Tehran's nuclear activity and ease Western sanctions.

India, Iran's top oil client after China, raised the imports to some of the highest levels in nearly two years in the first quarter, partly to make up for deep cuts in 2013 due to the lack of insurance coverage for refineries processing Iranian oil.

Intake rates have eased off since but are still running significantly higher than last year. Indian refiners shipped in 281,000 barrels per day (bpd) of oil from Iran between January and June, up from 211,400 bpd in the same period a year ago, data on tanker arrivals from trade sources shows.

In June, imports from Iran dropped by about a quarter from May to 167,300 bpd, the lowest in 10 months. The June intake was up about 19 percent from the same month last year.

India cut supplies from Iran by nearly 40 percent last year, the largest reduction by Iran's top clients - which besides China and India, includes Japan and South Korea.

China also boosted its imports after the temporary deal between Tehran and Western powers was signed in November last year, with imports from Iran rising by 50 percent in the first six months of this year.

Iran and six world powers agreed to a four-month extension of the temporary deal after missing a July 20 deadline to reach a final agreement on curbing Iran's nuclear programme in return for the end of sanctions.

Asian buyers are expected to import about 1.25 million to 1.3 million bpd of Iranian oil in the first half of the year, industry and government sources have said.

South Korea's imports from Iran fell 11 percent in the first half of the year, while Japan has yet to report is oil imports for June.

State-run Mangalore Refinery and Petrochemical Ltd was the biggest India client of Iranian oil in June followed by Essar Oil Ltd, the data showed. MRPL and Essar are India's only two regular monthly importers of Iranian crude.

Iran's share of total Indian oil imports rose to 7.3 percent in the first half of this year compared with 5.4 percent last year, the tanker arrival data also showed.

In the first half of the year India's import of oil from Latin America and Middle East has declined marginally while that from Africa has risen.

Overall, India shipped in 10.8 percent less crude in June than a year ago, the data showed. Total crude imports for the January-June period fell 1 percent.